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<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var a = 10 ;
        var b = 11 ;
        var c = a ;
        a = b;
        b = c;

        var arr = [1,2,3,4];
        // 交换23的位置
        var res = arr [1];
        arr [1] = arr [2];
        arr [2] = res;
        console.log(arr);
    </script>
</body>
</html>